There's not a lot of evidence for the existence of (a). (b) are quite common, and show up everywhere. Fridge magnets. Speakers. Electric motors. Etc. They may be useful in mag-lev trains. But there's nothing revolutionary about them.

Though it seems trivial at first, this magnet array seems frighteningly close to a magnetic monopole...

The only thing frightening about this triviality is that they successfully tricked you into thinking that it in any way resembles a magnetic monopole. No blame on your side: jargon doth make suckers of us all.

You might want to refer to Cecil's article about the Holy Grail. "You might as well search for Excalibur, or for Frodo's magic ring." Or a perpetual motion machine. AFAIK magnetic monopoles are in this category. Science does have some metaphorical 'holy grails', such as a Theory of Everything, but magnetic monopoles aren't something that serious scientists are looking for.

But then, legitimate physicists seem to talk of magnetic monopoles as if they exist but are very rare. (This is an example from ScienceWorld.) This says that the experimental upper limit is 1 monopole per 1029 nucleons. Rather than calculate the number of nucleons in a real superconductor (where these observations are made), I'll use carbon and say that there is, at most, one monopole per 109 moles of carbon, or one in each 110,000 metric tons. Perhaps physicists hold that magnetic monopoles exist, but are too rare to be applied practically. It would seem that they do not think they can be induced.

Is the (theoretic) compositional nature of monopoles understood? Are they something we could manufacture of we had the tools to manipulate matter all the way down to quark level, or are they thought to be some weird nonmaterial leftover of the big bang or something?

The only thing frightening about this triviality is that they successfully tricked you into thinking that it in any way resembles a magnetic monopole. No blame on your side: jargon doth make suckers of us all.

Halbach arrays are hardly a triviality (they have been sucessfuly used in particle accelerators, motors and maglev trains), but the comparison to a magnetic monopole is disingenuous. Halbach arrays concentrate the magnetic field to one side, so the magnet will stick on one side but not the other, but this field has + and - areas, same as any magnet.

Perhaps physicists hold that magnetic monopoles exist, but are too rare to be applied practically. It would seem that they do not think they can be induced.

Quote:

Originally Posted by Mangetout

Is the (theoretic) compositional nature of monopoles understood?

To take both of these together, while monopoles don't arise in the Standard Model, which handily describes all of particle physics to date*, it's known that they can arise in many generalisations of it, particularly in many proposed Grand Unified Theories (GUTs). The physics of such monopoles is rather well understood. Since most particle physicists expect that some such generalisation will be what eventually replaces the Standard Model, monopoles are very much something they expect might exist.
There are then various experimental and astrophysical limits on how many there could be. These all suggest that they're pretty rare. Furthermore, because of inflation, there are arguments that, if they do exist, there's only likely to be about 1 in the entire visible universe. So the concensus is possible, but very rare.

As for inducing/producing them, just promise me a laboratory source with particles energies of, oh, 1015 GeV and I'll see what I can do.

* I, naturally, mean a non-minimal SM with neutrino masses.

Quote:

Originally Posted by Roches

Science does have some metaphorical 'holy grails', such as a Theory of Everything, but magnetic monopoles aren't something that serious scientists are looking for.

Since it's always a hypothetical possibilty that monopoles exist for some other reason, which might make them more common, people have conducted direct searches for them. There is even an old case where one of these experiments seemed to have detected one. Because the experimenters couldn't repeat the observation, along with the expectation that they're rare, nobody now believes that what they saw was actually a monopole. I haven't checked, but it wouldn't surprise me if there are serious groups that are still looking, just in case - it's a longshot, but it's their career decision.

It's possible to make a configuration of magnets with more flux on one side than the other, but the configuration shown in the page the OP links wouldn't do it. And if it's so remarkably like a monopole that it freaks out the Wondermagnet staff, that says more about the Wondermagnet staff than it does about the configuration.

With that said, another potential Big Use for monopoles is energy generation. Many variants of the Standard Model predict that protons should eventually decay, though only after a very long time. They likewise predict that the presence of a magnetic monopole should greatly catalyze this decay. The particles into which a proton would decay are all much less massive than the proton, and if you also have electrons in the vicinity (as you presumably would) you could in principle decay completely into photons. So this would amount to effectively total E = mc2 generation, which is about as good as you're going to be able to get.

And speaking as a theorist, I also must point out that measurements of monopoles, if discovered, would teach us a lot about the inner workings of physics, and the search for monopoles is itself likely to give us a lot to chew on even if it doesn't actually come up with any. I should also point out that monopole detectors are exceedingly simple and inexpensive to construct, so it's even easier to justify spending money on them.

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